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Date: Mon, 7 Nov 2011 07:34:29 +1100
From: Cameron Simpson <cs@zip.com.au>
To: gene heskett <gheskett@wdtv.com>
Subject: Re: Python lesson please
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On 06Nov2011 13:14, gene heskett <gheskett@wdtv.com> wrote:
| Greetings experts:
| 
| I just dl'd the duqu driver finder script from a link to NSS on /., and 
| fixed enough of the tabs in it to make it run error-free.  At least python 
| isn't having a litter of cows over the indentation now.
| 
| But it also runs instantly on linux.
| 
| This line looks suspect to me:
|  rootdir = sys.argv[1]
| 
| And I have a suspicion it is null on a linux box.

That line collects the first command line argument. sys.argv is the
command line; argv[0] is the command name, argv[1] the first argument
and so forth.

Also, if there is no first argument then trying to access argv[1] will
raise an IndexError exception, not return a null value.

If you're this new to python, note that easy debugging statements can be
written:

  print >>sys.stderr, "the value of foo is", foo

and so forth.

Perhaps more relevantly:

If you have unmangled a lot of tabs, remember that control flow is
indentation based in python, and you may have broken some logic.
(For this reason a number of us set our editors to work only in spaces).

Anyway, while changing:

  statement1
  statement2

into:

  statement1
    statement2

will usually make python complain, changing:

  if some test here:
    statement1
    statement2

into:

  if some test here:
    statement1
  statement2

just means that statement2 is no longer inside the if-statement, and
elicit no compaints. But will elicit bugs!

Cheers,
-- 
Cameron Simpson <cs@zip.com.au> DoD#743
http://www.cskk.ezoshosting.com/cs/

The ZZR-1100 is not the bike for me, but the day they invent "nerf" roads
and ban radars I'll be the first in line......AMCN